LTD-4608JG 0.4-Inch Dual-Digit LED Display Datasheet - Character Height 10.0mm - Green - Technical Documentation

1. Product Overview

LTD-4608JG is a compact, high-performance dual-digit seven-segment display, specifically designed for applications requiring clear numeric display with low power consumption. Its primary function is to provide visual numeric output in electronic devices such as instrument panels, test equipment, consumer electronics, and industrial controls. The core advantage of this device lies in its LED chips, which utilize advanced AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material, offering higher efficiency and color purity compared to older technologies. The target market includes designers and engineers working on portable devices, battery-powered equipment, and any application with stringent constraints on space, power efficiency, and readability.

1.1 Main Features and Core Advantages

• 0.4-inch (10.0 mm) Character Height:Provides a character size suitable for medium-distance viewing, achieving a balance between visibility and component footprint.
• Continuous uniform segments:Ensure the displayed numbers have a smooth, professional appearance, with no visible gaps or irregularities when illuminated.
• Low power consumption requirements:Designed specifically for energy efficiency, it is an ideal choice for battery-powered devices. Under standard luminous intensity measurement, its typical forward operating current is 1mA.
• High Brightness and High Contrast:The combination of AlInGaP material and gray background with white segments creates excellent luminosity and sharp contrast, ensuring readability even under well-lit environmental conditions.
• Wide Viewing Angle:Consistent light output and color across a wide viewing angle enhance usability from various perspectives.
• Solid State Reliability:As an LED-based device, it offers a longer lifespan, impact resistance, and fast switching times compared to mechanical or other display technologies.
• Grading by Light Intensity:Devices are graded based on their light output to achieve consistent brightness matching in multi-digit or multi-device applications.

2. Technical Parameters: In-depth and Objective Interpretation

This section provides a detailed analysis of the electrical and optical characteristics defined in the datasheet, explaining their significance for design and application.

2.1 Absolute Maximum Ratings

These are stress limits that must not be exceeded under any conditions to prevent permanent damage to the device.

• Power consumption per segment:70 mW. This is the maximum power that a single LED segment can safely dissipate as heat.
• Peak forward current per segment:60 mA (at 1/10 duty cycle, 0.1ms pulse width). This rating is suitable for brief pulse operation and is useful for multiplexing or achieving higher instantaneous brightness.
• Continuous forward current per segment:25 mA (at 25°C). This is the maximum DC current for continuous operation. The datasheet specifies a derating factor of 0.33 mA/°C above 25°C, meaning the permissible continuous current decreases as the ambient temperature rises to manage thermal load.
• Reverse voltage per segment:5 V. Exceeding this voltage under reverse bias may damage the LED junction.
• Operating and storage temperature range:-35°C to +85°C. This device is suitable for industrial-grade temperature environments.
• Welding Temperature:260°C for 3 seconds, measured at a point 1/16 inch (approximately 1.6mm) below the package body. This defines the reflow soldering profile to avoid thermal damage during assembly.

2.2 Electrical and Optical Characteristics (at Ta=25°C)

These are typical performance parameters under specified test conditions.

• Average luminous intensity (Iv):At a forward current (IF) of 1mA, it is 320 to 850 µcd (min to max). This wide range indicates the binning process; designers must account for this variation or select binned parts for uniform appearance. Typical values are likely near the middle of this range.
• Peak Emission Wavelength (λp):571 nm (typical). This is the wavelength at which the emission intensity is highest, placing it in the pure green region of the visible spectrum.
• Spectral Line Half-Width (Δλ):15 nm (typical value). This measures spectral purity. The narrower the full width at half maximum, the more monochromatic and higher the saturation the color is.
• Dominant Wavelength (λd):572 nm (typical value). This is the single wavelength perceived by the human eye, which is very close to the peak wavelength of this device.
• Forward Voltage per Segment (VF):2.05V to 2.6V (typical) at IF=20mA. This is the voltage drop when the LED segment is conducting. It is crucial for designing the current limiting circuit. This variation is due to normal semiconductor manufacturing tolerances.
• Reverse Current per Segment (IR):100 µA (max) at VR=5V. This is the small leakage current when the LED is reverse-biased at its maximum rating.
• Iv-m (Luminous Intensity Matching Ratio):2:1 (Maximum). This parameter specifies the maximum allowable ratio between the brightest and darkest segments within a single device or between devices of the same bin, ensuring visual uniformity.

3. Explanation of the Grading System

The datasheet indicates that the device is "binned by luminous intensity." This refers to the sorting (binning) process after production.

• Luminous Intensity Binning:As indicated by the Iv range (320-850 µcd @1mA), LEDs are sorted into groups based on their measured light output. This allows the manufacturer to offer parts with a guaranteed minimum brightness, or to offer parts with a tighter intensity range at a higher price. Designers should specify the required bin or be prepared for brightness variation in the bill of materials.
• Wavelength/Color Grading:Although not explicitly stated with multiple codes, the tight typical specifications for λp (571nm) and λd (572nm) indicate a controlled manufacturing process. For critical color applications, parts with specific wavelength grading may be available.
• Forward Voltage Grading:VF range (2.05-2.6V) represents the natural distribution. For applications extremely sensitive to power supply design, selecting components with specific voltage grades may be beneficial.

4. Performance Curve Analysis

The datasheet references "Typical Electrical/Optical Characteristic Curves". Although specific graphs are not provided in the text, standard curves for such devices typically include:

• Relative luminous intensity vs. forward current (I-V curve):This graph shows how light output increases with current. It is typically linear at lower currents but may saturate at higher currents due to thermal effects. The 1mA test point of Iv indicates operation in the efficient, linear region.
• Forward voltage vs. forward current:It shows the exponential relationship, which is crucial for designing constant current drivers.
• Relative Luminous Intensity vs. Ambient Temperature:It demonstrates how light output decreases with increasing temperature. This is a key consideration in high-temperature environments.
• Spectral Distribution:The relationship between light intensity and wavelength, showing a peak at ~571nm and a narrow full width at half maximum, confirms pure green color.

5. Mechanical and Packaging Information

5.1 Package Dimensions and Drawings

The device is housed in a standard 10-pin Dual In-line Package (DIP). Key dimensional specifications from the datasheet: All dimensions are in millimeters unless otherwise noted, with a standard tolerance of ±0.25mm (0.01 inch). The drawing details overall length, width, height, digit spacing, segment dimensions, and pin pitch (likely the standard 0.1 inch / 2.54mm spacing).

5.2 Pin Connections and Polarity Identification

The device employsCommon anodeconfiguration for multiplexing. The internal circuit diagram shows two common anodes (one per digit) and independent cathodes for each segment (A-G and DP).

Pin arrangement:
1: Cathode C
2: Cathode D.P. (Decimal Point)
3: Cathode E
4: Common Anode (Digit 2)
5: Cathode D
6: Cathode F
7: Cathode G
8: Cathode B
9: Common Anode (Digit 1)
10: Cathode A

Polarity is clearly indicated by the "common anode" marking. The physical package may have a notch or dot near pin 1 for orientation identification.

6. Welding and Assembly Guide

• Reflow soldering parameters:According to the absolute maximum ratings, the recommended soldering profile is 260°C for 3 seconds, measured at a point 1.6mm below the package body. This is the standard lead-free reflow condition.
• Precautions:
  • Avoid applying mechanical stress to the pins during insertion.
  • Ensure control of the soldering iron tip temperature to prevent exceeding the package's maximum temperature.
  • If necessary, use appropriate flux and cleaning procedures.
• Storage Conditions:Store in a dry, anti-static environment within the specified temperature range (-35°C to +85°C). Avoid exposure to high humidity or corrosive gases.

7. Packaging and Ordering Information

• Packaging Specifications:Typically, such displays are supplied in anti-static tubes or trays to protect the pins and lens from damage and electrostatic discharge (ESD).
• Model Naming Rules:The part number LTD-4608JG likely follows an internal coding system, where "LTD" indicates the product series (LED display), "4608" denotes the size and type (0.4-inch 2-digit), and "JG" specifies the color (green). There may be other variants, such as those with a right-side decimal point (as described).

8. Application Suggestions

8.1 Typical Application Scenarios

• Digital Multimeter and Clamp Meter
• Bench Power Supply and Electronic Load
• Process Control Indicator
• Fitness Equipment Display
• Automotive Aftermarket Gauge (for in-vehicle use)
• Consumer Appliance Timers and Counters

8.2 Design Considerations

• Driver circuit:为每个阴极线路使用恒流驱动器或限流电阻。为了对两个数字进行多路复用，以足够高的频率（通常>60Hz）顺序切换共阳极（引脚4和9），以避免闪烁。
• Current calculation:Based on the required brightness and VF curve. For example, to achieve a typical brightness of 1mA with a 5V power supply and a VF of 2.3V, the current-limiting resistor is R = (V_supply - VF) / I_F = (5 - 2.3) / 0.001 = 2700 Ω.
• Microcontroller interface:If the current per segment is within the sink current capability of the MCU, the cathode can be driven directly by a microcontroller GPIO pin (sink current), or via a transistor/MOSFET array for higher current.
• Viewing angle:By installing the display perpendicular to the primary user's line of sight, its wide viewing angle is fully utilized.

9. Technical Comparison and Differentiation

Compared to older technologies (such as standard GaP green LEDs or red GaAsP LEDs), the AlInGaP-based LTD-4608JG offers:

• Higher efficiency and brightness:More light output per milliampere of current.
• Superior color saturation:Upana wa nusu ya wigo mwembamba hutoa kijani kibichi safi zaidi na kinachoonekana kwa macho.
• Utulivu bora wa joto:AlInGaP kwa kawaida huhifadhi utendaji wake vizuri zaidi katika anuwai ya joto kuliko baadhi ya nyenzo za zamani.
• Compared to modern white LED backlit LCDs, this device offers higher contrast in direct sunlight, consumes less power for simple digital displays, and features an extremely simple interface (direct drive vs. LCD controller).

10. Frequently Asked Questions (Based on Technical Parameters)

Q1: What is the purpose of a "Luminous Intensity Matching Ratio" of 2:1?
A1: This ratio ensures visual consistency. It means that within one display unit, the brightness of any segment will not exceed twice the brightness of the dimmest segment. This prevents uneven digital illumination, which could otherwise be mistaken for a different digit (e.g., a dimmer '8' might look like a '0').

Q2: Can I drive this display with a 3.3V microcontroller system?
A2: Yes, but careful design is required. The typical VF is 2.05-2.6V. With a 3.3V supply, the voltage headroom for the current-limiting resistor is very small (3.3 - 2.6 = 0.7V). You must calculate the resistor value precisely (e.g., for 1mA: R = 0.7V / 0.001A = 700Ω). Ensure the MCU pin can sink the required current. For low-voltage supplies, constant-current driver ICs are often a more reliable solution.

Q3: Why are there two different current ratings (continuous 25mA and peak 60mA)?
A3: The 25mA continuous rating is for DC operation, limited by average thermal dissipation. The 60mA peak rating allows for higher instantaneous brightness in multiplexed systems. In multiplexing, each digit is powered only part of the time (duty cycle). A higher peak current during its "on" time produces a brighter perceived average brightness, while the lower average current keeps the device within its thermal limits.

11. Case Studies on Practical Design and Usage

Case: Design a simple 2-digit voltmeter reading
A designer is creating a compact voltmeter to display 0.0V to 9.9V. They selected the LTD-4608JG for its small size, low power consumption, and clear green display. The system uses a microcontroller with an analog-to-digital converter (ADC) to measure voltage.

• Circuit Design:Port pins of the microcontroller are connected to the segment cathodes (A-G, DP) through 220Ω current-limiting resistors (calculated at approximately 3mA per segment at 5V). Two additional GPIO pins drive PNP transistors (or P-channel MOSFETs) to switch the common anodes (Digit 1 and Digit 2) to the 5V power supply.
• Software:The firmware reads the ADC, converts the value into two BCD digits, and uses a lookup table to determine which segments to illuminate for each digit (0-9). It then performs multiplexing: turns on the transistor for Digit 1, sets the cathode pattern for the first digit, waits 5ms, turns off Digit 1, turns on the transistor for Digit 2, sets the cathode pattern for the second digit, waits 5ms, and then repeats. This 100Hz refresh rate eliminates visible flicker.
• Results:A clear, stable two-digit reading, consuming minimal microcontroller resources and power.

12. Introduction to Working Principles

The LTD-4608JG operates based on the principle of electroluminescence in a semiconductor p-n junction. When a forward voltage exceeding the junction's built-in potential (approximately 2V for AlInGaP) is applied, electrons from the n-type region and holes from the p-type region recombine in the active region. In AlInGaP LEDs, this recombination primarily releases energy in the form of photons, with a wavelength corresponding to the green part of the spectrum (~571nm). The specific alloy composition of aluminum, indium, gallium, and phosphide determines the bandgap energy, thereby determining the color of the emitted light. The opaque GaAs substrate helps reflect light upward, improving the overall light extraction efficiency from the top surface. The seven segments are independent LED chips arranged in a digit pattern; by selectively powering combinations of these segments, any digit from 0 to 9 (and some letters) can be formed.

13. Technology Trends and Development

E ui o le fa'aaliga LED e fitu vaega ose fofo mautu ma taugofie mo le faitau numera, o le lautele lautele o tekinolosi fa'aaliga o lo'o fa'aauau pea ona atina'e. O fa'asologa e feso'ota'i ma lenei vaega o oloa e aofia ai:

• Efficiency Improvement:Ongoing research on semiconductor materials, including further improvements to AlInGaP and the development of materials like InGaN for other colors, continuously drives the enhancement of lumens-per-watt efficiency, enabling brighter displays at lower currents.
• Miniaturization:The relentless pursuit of smaller pixel pitch and higher density continues, although for standard seven-segment displays, the 0.4-inch size represents an established optimal balance point in many applications.
• Integration:Some modern displays integrate the driver IC or even a microcontroller interface (such as I2C or SPI) directly into the package, simplifying external circuit design. The LTD-4608JG represents the traditional, discrete approach, offering maximum flexibility and lower cost for high-volume, cost-sensitive designs.
• Competition from Alternative Technologies:OLED (Organic LED) displays offer excellent contrast and viewing angles, and are becoming increasingly affordable for small, custom-shaped displays. However, for simple, high-brightness, low-power digital indicators, traditional LED segment displays like the LTD-4608JG still maintain significant advantages in lifespan, ruggedness, and sunlight readability.